JP5852193B1 - User equipment - Google Patents

Abstract

The present invention provides a technique for avoiding a decrease in throughput due to duplicate transmission of downlink packets when split bearers are deleted. A transmission / reception unit that communicates simultaneously with a master base station and a secondary base station by dual connectivity, an RLC layer processing unit having an RLC layer for the master base station and an RLC layer for the secondary base station, and a master base A user equipment having a PDCP layer processing unit having a PDCP layer for transmitting and receiving data between an RLC layer for a station and an RLC layer for a secondary base station, wherein the RLC layer processing unit When the split bearer set for the base station is deleted, the re-establishment process is executed for the RLC layer for the secondary base station, and the split bearer is released after the re-establishment process is executed. [Selection] Figure 7

Description

  The present invention relates to a wireless communication system.

  Currently, as a next-generation communication standard of the LTE system, enhancement of functionality of LTE-Advanced is being promoted. In the LTE-Advanced system, carrier aggregation (CA) technology is introduced in order to achieve a throughput higher than that of the LTE system while ensuring backward compatibility with the LTE system. In carrier aggregation, a component carrier (CC) having a maximum bandwidth of 20 MHz supported by the LTE system is used as a basic component, and by using these multiple component carriers at the same time, wider bandwidth communication is realized. It is planned to do.

  In carrier aggregation, a user apparatus (User Equipment: UE) can communicate with a base station (evolved NodeB: eNB) using a plurality of component carriers simultaneously. In carrier aggregation, a highly reliable primary cell (Primary Cell: PCell) that ensures connectivity with user equipment and a secondary cell (Secondary Cell: SCell) that is additionally set in the user equipment connected to the primary cell Alternatively, a secondary cell group (SCG) is set.

  The primary cell is a cell similar to the serving cell of the LTE system, and is a cell for ensuring connectivity between the user apparatus and the network. On the other hand, the secondary cell or the secondary cell group is a cell or a cell group that is added to the primary cell and set in the user apparatus.

  In carrier aggregation up to LTE Release 10 (Rel-10), as shown in the left diagram of FIG. 1, it is defined that user apparatuses communicate simultaneously using a plurality of component carriers provided by the same base station. ing. On the other hand, in Rel-12, the carrier aggregation of Rel-10 is further expanded, and as shown in the right diagram of FIG. 1, the user apparatus performs simultaneous communication using a plurality of component carriers provided by a plurality of base stations. Dual connectivity (Dual Connectivity: DC) is being studied. For example, when all the component carriers cannot be accommodated in a single base station, it is considered that dual connectivity is effectively used in order to achieve the same throughput as Rel-10.

  In such dual connectivity, a split bearer is set. When a master base station or a macro base station (MeNB) is used as an anchor node that distributes a bearer, as shown in FIG. 2, the master base station transmits a downlink packet received from an S-GW (Serving Gateway). The packet is distributed to a packet transmitted to the user apparatus via its own cell and a packet transmitted to the user apparatus via the secondary base station (SeNB). When a split bearer with the master base station as an anchor node is set, as shown in FIG. 3, the user apparatus has a physical layer (PHY) for the master base station, a medium access control (MAC) layer (m− MAC) and RLC (Radio Link Control) layer (m-RLC), PHY layer for secondary base station, s-MAC layer and s-RLC layer, and m-RLC layer and s-RLC layer With PDCP layer. The packet received from the master base station and the packet received from the secondary base station are reordered in the PDCP layer and sent to the upper layer.

  Further, according to the LTE standard, re-establishment processing (re-establishment) is performed on the RLC layer and the PDCP layer at the time of handover or reconnection. In the re-establishment process of the RLC layer, the transmitting side of the RLC layer discards all RLC PDUs (Packet Data Units) to be transmitted, while the receiving side of the RLC layer receives RLC SDU ( The service data unit is re-assembled, and the configured RLC SDU is sent to the PDCP layer. Also, various timers used in the RLC layer are stopped and reset, and all the various variables are initialized.

  On the other hand, in the PDCP layer re-establishment process, the PDCP layer transmitting side retransmits PDCP PDUs that have not received acknowledgment (ACK) in the RLC layer, while the PDCP layer receiving side retransmits the RLC layer. The RLC SDU received by the establishment process and the RLC SDU newly transmitted after the re-establishment process are reordered. Here, the PDCP layer performs different control based on the reception window for reordering on the RLC SDU received by the re-establishment process of the RLC layer and the newly transmitted RLC SDU. That is, for the RLC SDU received by the re-establishment process of the RLC layer, the PDCP layer does not update the reception window when the PDCP sequence number of the received packet is discontinuous, while the newly transmitted RLC SDU On the other hand, the PDCP layer updates the reception window even when the PDCP sequence number of the received packet is discontinuous.

3GPP R2-131782

  When deleting a split bearer in dual connectivity, the above-described processing at the time of handover or reconnection is not executed. For example, as shown in FIG. 4, when the split bearer is deleted, in downlink communication, RLC PDUs # 1 to ## that are waiting for reordering due to the reception of RLC PDU # 0 by the s-RLC layer are not received. All 4 will be discarded. For this reason, after the split bearer is released, the master base station needs to retransmit not only RLC PDU # 0 waiting for reception but also RLC PDUs # 1 to # 4 received in the s-RLC layer of the user equipment. , Throughput decreases. In the split bearer, the downlink packet can be transmitted from both the master base station and the secondary base station. However, for the sake of simplicity of explanation, FIG. 4 shows a case where the packet is transmitted only from the secondary base station.

  In the split bearer, uplink communication from the user apparatus is performed while switching between two transmission directions of transmission to the master base station and transmission to the secondary base station by RRC signaling. At the time of switching the uplink transmission direction, re-establishment processing is not executed for the PDCP layer and the RLC layer at present. For this reason, as shown in FIG. 5, for example, PDCP PDUs # 0 to # 3 distributed to be transmitted to the secondary base station in uplink communication are uplink transmission directions from the secondary base station to the master base station. Even after the change, the data is still transmitted to the secondary base station. On the other hand, the secondary base station may stop receiving from the user equipment after the uplink transmission change instruction, and RLC PDUs # 0 to # 3 generated from PDCP PDUs # 0 to # 3 are unnecessary. Will be sent. For simplification of description, PDCP PDU: RLC PDU = 1: 1 is set in FIG. The user apparatus transmits packets after RLC PDU # 4 to the changed master base station. When the secondary base station does not receive RLC PDU # 0 to # 3, the master base station transmits RLC PDU # 0. RLC PDU # 4 is received prior to ~ # 3. Since the re-establishment process is not executed, the PDCP layer of the master base station discards RLC PDUs # 0 to # 3 that arrive thereafter from outside the reception window range.

  In view of the above-described problems, an object of the present invention is to provide a technique for avoiding a decrease in throughput due to duplicate transmission of downlink packets when split bearers are deleted.

  In order to solve the above-described problems, one feature of the present invention is that a transmitter / receiver that simultaneously communicates with a master base station and a secondary base station by dual connectivity, an RLC (Radio Link Control) layer for the master base station, and the secondary base RLC layer processing unit having an RLC layer for a station, and a PDCP (Packet Data Convergence Protocol) layer for transmitting and receiving data between the RLC layer for the master base station and the RLC layer for the secondary base station The RCP layer processing unit, when deleting the split bearer set for the secondary base station, the RLC layer processing unit to the RLC layer for the secondary base station for The present invention relates to a user apparatus that executes re-establishment processing and releases the split bearer after execution of the re-establishment processing.

  According to the present invention, it is possible to avoid a decrease in throughput due to duplicate transmission of downlink packets when split bearers are deleted.

FIG. 1 is a schematic diagram illustrating carrier aggregation. FIG. 2 is a schematic diagram showing a split bearer having a macro base station as an anchor node. FIG. 3 is a diagram illustrating a layer configuration for downlink communication at the time of setting a split bearer. FIG. 4 is a schematic diagram showing a process when a conventional split bearer is deleted. FIG. 5 is a schematic diagram showing a conventional process when changing the uplink transmission direction. FIG. 6 is a schematic diagram illustrating a wireless communication system according to an embodiment of the present invention. FIG. 7 is a block diagram illustrating a configuration of a user apparatus according to an embodiment of the present invention. FIG. 8 is a schematic diagram showing a process when deleting a split bearer according to the first embodiment of the present invention. FIG. 9 is a schematic diagram illustrating a reordering process in the PDCP layer during a conventional RLC layer re-establishment process. FIG. 10 is a schematic diagram illustrating the reordering process in the PDCP layer during the RLC layer re-establishment process according to the first embodiment of the present invention. FIG. 10 is a flowchart showing split bearer deletion processing in the RLC layer processing unit according to the first embodiment of the present invention. FIG. 12 is a flowchart showing split bearer deletion processing in the PDCP layer processing unit according to the first embodiment of the present invention. FIG. 13 is a flowchart showing an uplink transmission direction change process in the user apparatus according to the second embodiment of the present invention. FIG. 14 is a block diagram illustrating a configuration of a base station according to the second embodiment of the present invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  In an embodiment to be described later, a user equipment and a base station that support dual connectivity are disclosed. In summary of an embodiment to be described later, when a split bearer set for a secondary base station is deleted in downlink communication of the split bearer, the user apparatus executes re-establishment processing for the s-RLC layer. The s-RLC layer does not discard RLC PDUs waiting for reordering, configures RLC SDUs as much as possible, and transmits them to the PDCP layer. Further, the user apparatus performs a re-establishment process on the PDCP layer, and the PDCP layer uses the reordering timer to out-of-the RLC SDU (PDCP PDU) received until the reordering timer expires. Even if the sequence is not resolved, the PDCP PDU waiting for reordering is sent to the upper layer. Thereby, even when the missing RLC PDU is not transmitted to the user apparatus due to discarding or the like, it is possible to avoid a situation in which the PDCP PDU waiting for reordering cannot be transmitted to the upper layer.

  In another example, in split bearer uplink communication, the user equipment performs re-establishment processing on the RLC layer and the PDCP layer when changing the transmission direction of the uplink data packet. As a result, the user apparatus can stop transmission of the data packet allocated in the transmission direction before the change, and can transmit the untransmitted data packet in-sequence to the base station after the change.

  A radio communication system according to an embodiment of the present invention will be described with reference to FIG. FIG. 6 is a schematic diagram illustrating a wireless communication system according to an embodiment of the present invention.

  As illustrated in FIG. 6, the wireless communication system 10 includes a user apparatus 100 and base stations 200A and 200B. The radio communication system 10 supports dual connectivity in which the user apparatus 100 communicates simultaneously using component carriers CC # 1 and CC # 2 provided by a plurality of base stations 200A and 200B, and as illustrated, the user apparatus 100 communicates between the master base station (MeNB) 200A and the secondary base station (SeNB) 200B by using the dual connectivity function. In the illustrated embodiment, only two base stations 200 </ b> A and 200 </ b> B are shown, but in general, a large number of base stations 200 are arranged to cover the service area of the wireless communication system 10.

  The user apparatus 100 has a dual connectivity function for simultaneous communication with a plurality of base stations 200A and 200B. Typically, the user apparatus 100 may be any appropriate information processing apparatus having a wireless communication function such as a smartphone, a mobile phone, a tablet, a mobile router, and a wearable terminal as illustrated. The user apparatus 100 includes a CPU (Central Processing Unit) such as a processor, a memory apparatus such as a RAM (Random Access Memory) and a flash memory, a wireless communication apparatus for transmitting and receiving radio signals to and from the base stations 200A and 200B, and the like. Composed. For example, each function and process of the user device 100 described later may be realized by the CPU processing or executing data or a program stored in the memory device. However, the user apparatus 100 is not limited to the hardware configuration described above, and may be configured by a circuit that realizes one or more of the processes described below.

  Base stations 200 </ b> A and 200 </ b> B (hereinafter may be collectively referred to as base station 200) are networks such as upper stations and servers that are connected to a core network (not shown) by wireless connection with user apparatus 100. The downlink (DL) packet received from the device is transmitted to the user device 100, and the uplink (UL) packet received from the user device 100 is transmitted to the network device. In the illustrated embodiment, the base station 200A functions as a master base station (MeNB) or a primary base station, and the base station 200B functions as a secondary base station (SeNB). In dual connectivity, the master base station 200A controls simultaneous communication between the user apparatus 100 and the base stations 200A and 200B by dual connectivity and also controls communication with a higher-level core network (not shown). . The base station 200 typically includes an antenna for transmitting and receiving a radio signal to and from the user apparatus 100, a communication interface for communicating with the adjacent base station 200, and the base station 200 adjacent to the user apparatus 100. It is comprised by hardware resources, such as a processor and a circuit for processing the transmission / reception signal between. Each function and process of the base station 200 to be described later may be realized by a processor processing or executing data or a program stored in a memory device. However, the base station 200 is not limited to the hardware configuration described above, and may have any other appropriate hardware configuration.

  Next, the configuration of the user apparatus according to an embodiment of the present invention will be described with reference to FIG. FIG. 7 is a block diagram illustrating a configuration of a user apparatus according to an embodiment of the present invention.

  As illustrated in FIG. 7, the user apparatus 100 includes a transmission / reception unit 110, an RLC layer processing unit 120, and a PDCP layer processing unit 130.

  The transmission / reception unit 110 communicates simultaneously with the master base station 200A and the secondary base station 200B by dual connectivity. Specifically, the transmission / reception unit 110 transmits / receives various radio channels such as an uplink / downlink control channel and an uplink / downlink data channel to / from the master base station 200A and the secondary base station 200B.

  The RLC layer processing unit 120 includes an RLC (m-RLC) layer 121 for the master base station 200A and an RLC (s-RLC) layer for the secondary base station 200B. In the downlink communication using the split bearer, the m-RLC layer 121 configures an RLC SDU from the RLC PDU received from the master base station 200 </ b> A and transmits the RLC SDU to the PDCP layer processing unit 130. On the other hand, the s-RLC layer 122 configures an RLC SDU from a packet (RLC PDU) received from the secondary base station 200 </ b> B and transmits the RLC SDU to the PDCP layer processing unit 130. In uplink communication using split bearers, the m-RLC layer 121 configures an RLC PDU from the PDCP PDU received from the PDCP layer processing unit 130 and transmits the RLC PDU to the master base station 200A via a lower layer (not shown). . On the other hand, the s-RLC layer 122 forms an RLC PDU from the packet PDCP PDU received from the PDCP layer processing unit 130, and transmits the RLC PDU to the secondary base station 200B via a lower layer (not shown).

  The PDCP layer processing unit 130 includes a PDCP layer 131 that transmits and receives data between the m-RLC layer 121 for the master base station 200A and the s-RLC layer 122 for the secondary base station 200B. In downlink communication using split bearers, the PDCP layer 131 receives RLC SDUs from the m-RLC layer 121 and the s-RLC layer 122 and reorders the received packets based on the sequence number (SN) of each packet. Transmit to upper layer (not shown). In the reordering process, the PDCP layer processing unit 130 uses the reception window, and the packet received by the reestablishment process from the RLC layer does not update the reception window when the sequence number is discontinuous. For a newly transmitted packet instead of processing, even if the sequence number is discontinuous, the transmitting base station 200A or 200B determines that the packet has been discarded, and updates the reception window. In uplink communication using split bearers, the PDCP layer 131 distributes a PDCP PDU to be transmitted into a packet to be transmitted to the master base station 200A and a packet to be transmitted to the secondary base station 200B, and the distributed packet is m-RLC. Transmit to the layer 121 and the s-RLC layer 122.

  Next, split bearer deletion processing according to the first example of the present invention will be described with reference to FIGS. As described above with reference to FIG. 4, in the conventional split bearer deletion process, all packets waiting for reordering in the s-RLC layer 122 are discarded before deletion, and after the split bearer is deleted from the secondary base station 200B. The master base station 200A has to retransmit the discarded packet. According to the first embodiment of the present invention, as illustrated in FIG. 8, the RLC layer processing unit 130 can start from a packet (RLC-PDU) waiting for reordering of the s-RLC layer 122 before deleting the split bearer. RLC SDUs are configured as long as possible and transmitted to the PDCP layer processing unit 130. Thereby, after deleting the split bearer for the secondary base station 200B, the master base station 200A only has to retransmit only the packet waiting for reception, and it is possible to avoid a decrease in throughput.

  In the first embodiment, when deleting the split bearer set for the secondary base station 200B, the RLC layer processing unit 120 performs re-establishment processing on the s-RLC layer 122 for the secondary base station 200B. And release the split bearer after the re-establishment process. For example, in the LTE standard, when a split bearer deletion instruction is received from the master base station 200A or the secondary base station 200B, the RLC layer processing unit 120 applies to the s-RLC layer 122 set in the secondary cell group (SCG). Execute re-establishment, and then release the split bearer.

  In one embodiment, the RLC layer processing unit 120 may transmit data packets that stay in the s-RLC layer 122 for the secondary base station 200B or SCG in the re-establishment process to the PDCP layer processing unit 130. For example, the staying data packet is an RLC packet data unit (RLC PDU) waiting for reordering in the s-RLC layer 122 for the secondary base station 200B or SCG, and the RLC layer processing unit 120 waits for the reordering. RLC service data units (RLC SDUs) may be configured from the RLC PDUs of the RCP PDUs and transmitted to the PDCP layer processing unit 130. When constructing an RLC service data unit (RLC SDU) from the RLC packet data unit waiting for reordering, the RLC layer processing unit 120 uses the RLC PDU waiting for reordering in the same manner as the reestablishment processing at the time of handover or reconnection. The RLC SDU is re-assembled as much as possible, and the configured RLC SDU is sent to the PDCP layer processing unit 130.

  In addition, in one embodiment, when the release of the split bearer is deletion for each EPS (Evolved Packet System) bearer, the RLC layer processing unit 120 performs the processing for the secondary base station 200B or the s-RLC layer 122 for SCG. The designated EPS bearer may be deleted without executing the re-establishment process. That is, in the LTE standard, when the release of the split bearer is deletion for each EPS bearer, the RLC layer processing unit 120 causes the secondary base station 200B or the s-RLC layer 122 for SCG to execute re-establishment. Alternatively, the RLC SDU may not be configured from the RLC PDU waiting for reordering and transmitted to the PDCP layer processing unit 130.

  As described above, the RLC layer processing unit 120 executes re-establishment processing on the s-RLC layer 122 when deleting the split bearer, and discards the RLC PDU waiting for reordering from the RLC PDU. Configure RLC SDUs as much as possible. At this time, the conventional PDCP layer changes the processing of the received PDCP PDU in accordance with the operation of the lower layer, and performs different operations such as waiting for reordering or discarding the lost packet, for example. When the re-establishment process is executed for the s-RLC layer 122 as described above, an unnecessary reordering wait occurs when reordering is performed in the same manner as in the past. For example, as illustrated in FIG. 9, when the PDCP layer processing unit 130 receives RLC SDUs # 1 to # 4 reconfigured from the s-RLC layer 122, the PDCP layer processing unit 130 performs mastering for reordering. Reception of RLC SDU # 0 retransmitted from base station 200A is waited for. When master base station 200A discards RLC SDU # 0, PDCP layer processing section 130 cannot receive RLC SDU # 0 and sends RLC SDUs # 1 to # 4 waiting for reordering to an upper layer. I can't do that. For this reason, even when the re-establishment process is performed on the s-RLC layer 122, it is not desirable from the viewpoint of performance that the PDCP layer processing unit 130 performs the reordering as in the related art.

  For this reason, according to the first embodiment of the present invention, the PDCP layer processing unit 130 has a reordering timer that is started in response to detection of an out-of-sequence of a data packet, and the s-RLC layer 122 Regardless of whether or not the re-establishment process is executed, the reordering timer is used to control the reordering of the packet received from the RLC layer processing unit 120. Specifically, when the reordering timer expires, the PDCP layer processing unit 130 transmits the data packet waiting for reordering received from the RLC layer processing unit 120 to the upper layer. For example, as illustrated in FIG. 10, when the PDCP layer processing unit 130 receives RLC SDUs # 1 to # 4 from the s-RLC layer 122, the PDCP layer processing unit 130 detects the lack of RLC SDU # 0. Start the reordering timer. If RLC SDU # 0 cannot be received before the reordering timer expires, PDCP layer processing section 130 sends RLC SDUs # 1 to # 4 waiting for reordering to the upper layer. As a result, even when the master base station 200A discards the RLC SDU # 0, the PDCP layer processing unit 130 can transmit the RLC SDUs # 1 to # 4 to the upper layer when the reordering timer expires. It becomes possible.

  In one embodiment, the PDCP layer processing unit 130 transmits a data packet waiting for reordering received from the RLC layer processing unit 120 along with the re-establishment processing for the m-RLC layer 121 for the master base station 200A. And the reordering timer may be controlled in accordance with the result of the determination. For example, if the data packet waiting for reordering is not transmitted along with the re-establishment process for the m-RLC layer 121 for the master base station 200A, in other words, the re-establishment process is performed for the s-RLC layer 122. In the normal case where the reordering timer is expired, the PDCP layer processing unit 130 transmits the data packet waiting for reordering received from the RLC layer processing unit 120 to the upper layer when the reordering timer expires. .

  On the other hand, if the data packet waiting for reordering is transmitted along with the re-establishment process for the m-RLC layer 121 for the master base station 200A, the PDCP layer processing unit 130 Execute reordering process. Specifically, the PDCP layer processing unit 130 reorders the data packet received by the re-establishment process using the reception window and the data packet newly transmitted after deleting the split bearer, and receives the data received by the re-establishment process. When there is a missing packet, the reception window is not updated, and when there is a missing data packet newly transmitted, the reception window is updated. When receiving a data packet within the range of the reception window, the PDCP layer processing unit 130 updates the reception window with the sequence number of the received data packet, and when receiving a data packet outside the range of the reception window, the data packet Is discarded. Thus, even if the RLC SDU waiting for reception is discarded from the master base station 200A, the PDCP layer processing unit 130 uses the reordering timer to receive the RLC received by the re-establishment processing for the s-RLC layer 122. SDUs can be sent to higher layers.

  FIG. 11 is a flowchart showing split bearer deletion processing in the RLC layer processing unit according to the first embodiment of the present invention.

  As illustrated in FIG. 11, in step S <b> 101, the master base station 200 </ b> A sets a split bearer for the user apparatus 100. The split bearer setting instruction may be notified by RRC signaling, for example.

  In step S102, the master base station 200A instructs the user apparatus 100 to delete the split bearer. The split bearer deletion instruction may be notified by RRC signaling, for example.

  In step S <b> 103, the RLC layer processing unit 120 executes re-establishment processing (re-establishment) on the s-RLC layer 122. Specifically, the RLC layer processing unit 120 configures RLC SDUs as much as possible from RLC PDUs waiting for reordering in the s-RLC layer 122 and sends them to the PDCP layer processing unit 130.

  In step S104, the RLC layer processing unit 120 releases the s-RLC layer 122.

  FIG. 12 is a flowchart showing split bearer deletion processing in the PDCP layer processing unit according to the first embodiment of the present invention.

  As illustrated in FIG. 12, in step S <b> 201, the master base station 200 </ b> A sets a split bearer for the user apparatus 100. The split bearer setting instruction may be notified by RRC signaling, for example.

  In step S202, when receiving the split bearer deletion instruction from the master base station 200A, the PDCP layer processing unit 130 is configured from the RLC PDU waiting for reordering from the RLC layer processing unit 120 in response to the split bearer deletion instruction. Receive RLC SDU.

  In step S <b> 203, the PDCP layer processing unit 130 determines whether the received RLC SDU is transmitted along with the re-establishment process for the m-RLC layer 121. When the received RLC SDU is transmitted along with the re-establishment process for the m-RLC layer 121 (S203: Yes), in step S204, the PDCP layer processing unit 130 reorders at the time of handover or reconnection. Execute the process.

  On the other hand, when the received RLC SDU is not transmitted along with the re-establishment process for the m-RLC layer 121 (S203: No), in step S205, the PDCP layer processing unit 130 executes the split bearer reordering process. To do. That is, the PDCP layer processing unit 130 activates the reordering timer when the sequence number of the received RLC SDU is discontinuous. When the missing RLC SDU cannot be received before the expiration of the reordering timer, the PDCP layer processing unit 130 configures a PDCP SDU from the RLC SDU waiting for reordering (PDCP PDU) and transmits the PDCP SDU to the upper layer.

  Next, the split bearer uplink transmission direction change process according to the second embodiment of the present invention will be described with reference to FIGS. As described above with reference to FIG. 5, in the conventional uplink transmission direction change process, the data packet allocated in the transmission direction before the change from the PDCP layer (in the example of FIG. 5, the RLC PDU of the s-RLC layer 122). # 0 to # 3) are transmitted to the base station 200 before the change (in the example of FIG. 5, the secondary base station 200B) even after the uplink transmission direction is changed, and may not be properly received. According to the second embodiment of the present invention, when the uplink transmission direction is changed in the split bearer, the RLC layer processing unit 120 and the PDCP layer processing unit 130 are reestablished for the RLC layer and the PDCP layer, respectively. Execute the process. Thereby, the user apparatus 100 can stop the transmission of the data packet allocated in the transmission direction before the change, and can transmit the untransmitted data packet to the base station 200 after the change in sequence.

  In the second embodiment, when changing the transmission direction of the uplink data packet in the split bearer set for the master base station 200A and the secondary base station 200B, the RLC layer processing unit 120 The re-establishment process is executed on the m-RLC layer 121 for the secondary base station 200B and the s-RLC layer 122 for the secondary base station 200B, and the PDCP layer processing unit 130 executes the re-establishment process on the PDCP layer 131 . For example, in the LTE standard, when an uplink transmission direction change instruction is received from the master base station 200A or the secondary base station 200B, the RLC layer processing unit 120 re-registers the m-RLC layer 121 and the s-RLC layer 122 with each other. -Establishment is executed, and the PDCP layer processing unit 130 executes re-establishment on the PDCP layer 131.

  In one embodiment, the RLC layer processing unit 120 and the PDCP layer processing unit 130 stop transmitting uplink data packets allocated before the transmission direction is changed, and transmit the uplink data packets that have been stopped to be transmitted in the transmission direction. Re-establishment processing may be performed on the RLC layers 121 and 122 and the PDCP layer 131 so as to be transmitted to the base station 200 to be changed. In this case, for example, the RLC layer processing unit 120 and the PDCP layer processing unit 130 may transmit the uplink data packets whose transmission has been stopped in the order of the sequence numbers, Re-establishment processing may be performed on As a result, an untransmitted uplink data packet can be transmitted in-sequence to the change-destination base station 200, and the data packet with the old sequence number arrives first at the change-destination base station 200. Accordingly, it is possible to avoid the possibility that the data packet having the younger sequence number is discarded as being out of the reception window range.

  In one embodiment, upon receiving an instruction for re-establishment processing from the base station 200 before changing the transmission direction, the RLC layer processing unit 120 and the PDCP processing unit 130 may execute the re-establishment processing. That is, some base stations 200 may continue to receive data packets even after the transmission direction is changed, and re-establishment processing may not be necessary. For this reason, when the base station 200 in the transmission direction before the change can receive the data packet even after the change in the transmission direction, the base station 200 notifies the user apparatus 100 of the necessity of the re-establishment process. It may be. For example, the RLC layer processing unit 120 and the PDCP processing unit 130 execute the re-establishment process only when the base station 200 in the transmission direction before the change instructs the re-establishment process. In other cases, the re-establishment process is performed. It may not be executed. Alternatively, the RLC layer processing unit 120 and the PDCP layer processing unit 130 do not execute the re-establishment process only when the base station 200 in the transmission direction before the change instructs not to perform the re-establishment process, and in other cases A re-establishment process may be executed. According to the present embodiment, unnecessary re-establishment processing can be avoided.

  Also, in one embodiment, the re-establishment process may be performed for uplink communication only. When changing the uplink transmission direction in the split bearer, the RLC layer processing unit 120 and the PDCP layer processing unit 130 perform re-establishment processing only for the part related to uplink communication with respect to the RLC layers 121 and 122 and the PDCP layer 131. You may make it perform. If the re-establishment process is executed for the part related to the downlink communication, the downlink communication is interrupted, and this is avoided. Specifically, the user apparatus 100 performs the re-establishment process only on the part related to the transmission side of the RLC layer and the PDCP layer, and the base station 200 applies only to the part related to the reception side of the RLC layer and the PDCP layer. Alternatively, the re-establishment process may be executed.

  FIG. 13 is a flowchart showing an uplink transmission direction change process in the user apparatus according to the second embodiment of the present invention.

  As illustrated in FIG. 13, in step S <b> 301, the user apparatus 100 sets a split bearer for the non-anchor base station 200 in response to a setting instruction from the anchor base station 200. The split bearer setting instruction may be notified by RRC signaling, for example.

  In step S302, the user apparatus 100 receives an uplink transmission direction change instruction. The uplink transmission direction change instruction may be notified by RRC signaling, for example.

  In step S303, the RLC layer processing unit 120 and the PDCP layer processing unit 130 perform re-establishment processing on the m-RLC layer 121, the s-RLC layer 122, and the PDCP layer 131, respectively. In one embodiment, the RLC layer processing unit 120 and the PDCP layer processing unit 130 stop transmission of the uplink data packet allocated before the transmission direction is changed, and transmit the stopped uplink data packet to the sequence number. The re-establishment process may be performed on the RLC layers 121 and 122 and the PDCP layer 131 so as to transmit to the base station 200 to which the transmission direction is changed in order.

  FIG. 14 is a block diagram illustrating a configuration of a base station according to the second embodiment of the present invention. The base station according to the present embodiment has an uplink reordering timer in the PDCP layer. When the uplink transmission direction of the split bearer is changed, the uplink reordering timer is activated, and the uplink reordering timer is being activated. Suspends transmission of data packets received from the user equipment to the upper layer until the sequence numbers are consecutive.

  As illustrated in FIG. 14, the base station 200 includes a transmission / reception unit 210, an RLC layer processing unit 220, and a PDCP layer processing unit 230.

  The transmission / reception unit 210 communicates with the user apparatus 100 by dual connectivity. Specifically, the transmission / reception unit 210 transmits / receives various radio channels such as an uplink / downlink control channel and an uplink / downlink data channel to / from the user apparatus 100.

  The RLC layer processing unit 220 includes an RLC layer 221 for communication with the user apparatus 100. In uplink communication using split bearers, the RLC layer processing unit 220 configures RLC SDUs from RLC PDUs received from the user apparatus 100 via the lower layer, and when the base station 200 is an anchor node of the split bearer, the configured RLC The SDU is transmitted to the PDCP layer processing unit 230 of the own station. On the other hand, when the base station 200 is not a split bearer anchor node, the configured RLC SDU is transmitted to the PDCP layer processing unit 230 of the anchor base station 200.

  The PDCP layer processing unit 230 has a PDCP 231 layer for communication with the user apparatus 100. In uplink communication using split bearers, when the base station 200 is an anchor node of a split bearer, the PDCP layer processing unit 230 receives the RLC SDU received from the RLC layer processing unit 220 of the own station and the other in which the split bearer is set. The RLC SDU received from the RLC layer processing unit 220 of the base station 200 is reordered to form a PDCP SDU and transmitted to the upper layer.

  The PDCP layer processing unit 230 has an uplink reordering timer, and activates the uplink reordering timer when changing the transmission direction of the uplink data packet in the split bearer set for the user apparatus 100. If the sequence number of the uplink data packet received from the user apparatus 100 is discontinuous, the transmission of the received uplink data packet to the upper layer is suspended.

  In one embodiment, the PDCP layer processing unit 230 determines the received uplink data packet if the sequence number of the uplink data packet received from the user equipment 100 by the expiration of the uplink reordering timer remains discontinuous. You may transmit to an upper layer. That is, when the uplink data packet that is missing by the expiration of the uplink reordering timer cannot be received from the user apparatus 100, the PDCP layer processing unit 230 abandons reception of the missing uplink data packet, An uplink data packet waiting for reordering is transmitted to an upper layer.

  On the other hand, when the uplink data packet corresponding to the missing sequence number is received, the PDCP layer processing unit 230 stops the uplink reordering timer and transmits the received uplink data packet to the upper layer. That is, when the uplink data packet that is missing before the expiration of the uplink reordering timer is received from the user apparatus 100, the PDCP layer processing unit 230 receives the received uplink data packet and the uplink data packet waiting for reordering. Are reordered and transmitted to the upper layer.

  The difference between the reordering timer defined in the split bearer and the uplink reordering timer is that the former reordering timer is always used for reordering, while the latter uplink reordering timer is used in the uplink transmission direction. It means that it is used only at a specific timing when changing. That is, when the PDCP layer processing unit 230 detects a missing sequence number for an uplink data packet received after expiration or stop of the uplink reordering timer, an uplink data packet corresponding to the missing sequence number is detected. It is determined that the user apparatus 100 has been discarded.

  Note that the first and second embodiments described above may be used separately or in combination. For example, when a split bearer is applied, the first embodiment may be applied to downlink communication, and the second embodiment may be applied to uplink communication. That is, in the downlink communication, when the split bearer set for the secondary base station 200B is deleted, the user apparatus 100 performs re-establishment processing on the s-RLC layer 122 for the secondary base station 200B. Execute and release the split bearer after executing the re-establishment process, while in uplink communication, the transmission direction of the uplink data packet in the split bearer set for the master base station 200A and the secondary base station 200B When changing, the user apparatus 100 may perform re-establishment processing on the m-RLC layer 121 for the master base station 200A and the s-RLC layer 122 and the PDCP layer 131 for the secondary base station 200B. Good.

  As mentioned above, although the Example of this invention was explained in full detail, this invention is not limited to the specific embodiment mentioned above, In the range of the summary of this invention described in the claim, various deformation | transformation・ Change is possible.

DESCRIPTION OF SYMBOLS 10 Radio | wireless communications system 100 User apparatus 110,210 Transmission / reception part 120,220 RLC layer process part 130,230 PDCP layer process part 200 Base station

Claims (10)

A transmitter / receiver that communicates simultaneously with the master base station and the secondary base station by dual connectivity,
An RLC layer processing unit having an RLC (Radio Link Control) layer for the master base station and an RLC layer for the secondary base station;
A PDCP layer processing unit having a PDCP (Packet Data Convergence Protocol) layer for transmitting and receiving data between the RLC layer for the master base station and the RLC layer for the secondary base station;
A user device comprising:
When the split bearer set for the secondary base station is deleted, the RLC layer processing unit executes a re-establishment process for the RLC layer for the secondary base station, and executes the re-establishment process. User equipment that releases the split bearer later.   The user apparatus according to claim 1, wherein the RLC layer processing unit transmits a data packet staying in an RLC layer for the secondary base station to the PDCP layer processing unit in the re-establishment process. The staying data packet is an RLC packet data unit waiting for reordering in an RLC layer for the secondary base station,
The user apparatus according to claim 2, wherein the RLC layer processing unit configures an RLC service data unit from the RLC packet data unit waiting for reordering, and transmits the RLC service data unit to the PDCP layer processing unit.   When the release of the split bearer is deletion for each EPS (Evolved Packet System) bearer, the RLC layer processing unit is designated without performing re-establishment processing for the RLC layer for the secondary base station. The user apparatus according to claim 1, wherein the EPS bearer is deleted. The PDCP layer processing unit has a reordering timer that is started in response to detection of an out-of-sequence of a data packet;
5. The user apparatus according to claim 1, wherein when the reordering timer expires, the PDCP layer processing unit transmits a data packet waiting for reordering received from the RLC layer processing unit to an upper layer.   The PDCP layer processing unit determines whether the data packet waiting for reordering received from the RLC layer processing unit is transmitted along with the re-establishment processing for the RLC layer for the master base station, and The user apparatus according to claim 5, wherein the reordering timer is controlled according to a result.   If the data packet waiting for reordering is not transmitted along with the re-establishment process for the RLC layer for the master base station, the PDCP layer processing unit, when the reordering timer expires, the RLC layer processing unit The user apparatus according to claim 6, wherein the data packet waiting for reordering received from is transmitted to an upper layer.   When the data packet waiting for reordering is transmitted along with the re-establishment process for the RLC layer for the master base station, the PDCP layer processing unit executes the reordering process at the time of handover or reconnection The user device according to claim 6 or 7.   When changing the transmission direction of the uplink data packet in the split bearer set for the master base station and the secondary base station, the RLC layer processing unit, the RLC layer for the master base station and the The re-establishment process is performed with respect to the RLC layer for the secondary base station, and the PDCP layer processing unit performs the re-establishment process with respect to the PDCP layer. User device.   The re-establishment process stops the transmission of uplink data packets after the change of the transmission direction, and transmits the uplink data packet whose transmission has been stopped to the base station to which the transmission direction is changed, and the RLC layer The user apparatus according to claim 9, wherein a PDCP layer is set.

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